Precipitation process



ly 1 1930- R. w. SHAFDR in AL 1,769,469

' PRECIPITATION rxocss's Filed July 19, 1924 [LIME I I MOLASSES COLD TREATMENT FILTRATION F 1 COLD WASTE COLD SACCHARATE WATER PRECIPITATE HOT TR EATMEN'f FILTRATION HOT WASTE I 01" SACCHARAT PRECIPITATE UNIT,

mum OFFICE- IRALPH W; SHAFOR, ALPHEUS R. EES, AND ROBERT J. BROWN,OF DENVER, COLORADO PRECIPITATION PROCESS Application fi led July 19, 1924. Sam No. 727,088.

'Our invention relates to a method of re% covering sugar from molasses icommonly known in the beet sugar industry as the Steffens process and it bears moreparticularly on the stepof the process in whichthe sugar contents of a mother liquor known as cold waste water, are recovered by forming a precipitate of the-lime and sucrose in the liquor, commonly referred to as the' hot saccharate precipitate.

It is the primary object of the present invention to facilitate and expedite the re-. covery of the sugar contents of the cold.

waste liquor obtained 'in the Stefi'ens pro cess of treating'molasses, by an operation in which the precipitate of lime and sucrose is produced under certain physical conditions which greatly increasevthe rate of sedimentation of the precipitated particles ;in the final step of separating the precipitate from the mother liquor, a

The above stated result is obtained by causing the sucrose and lime'to form into crystals or fiocs of comparatively large size while they are being precipitated under the influence of heat, and the formation of the larger crystals is produced by suitable dilution of the material under treatment, infla continuous operation. In order to facilitate the detailed'ceX-. plana-ti'on of our improved process and of the actions and results have shown in v V Y Figure, 1 of the accompanying drawings a diagrammatical' representation ofxthe Stefi'ens process of recovering sugar from" molasses, in which our improved method of producingthe hot'saccharate precipitate is included and 51 V apparatus suitable for carrying' the method into effect. fa 7 f .Referringto Figure 1- of the drawings,

the beet molasses obtained 'as' a byproduct during" crystallization of beetsugar from impure solutions of'the sugaf infthemain beet sugar: refining J system,' ar1e diluted with water and mixed while cooled with, p0wdered calcium oxidetoproduce'aprecipitatei of :tri-calcium' saccharate (3GaO=.C1gHaO obtained therein we Figure 2 represents in vertical sectionan- The precipitate is subsequently separated from the mother liquor known as the cold waste water. This cold wastewater usually contains in addition to impurities, 7 from 0,55% to 1.0% sugar and'some lime and in order to recover this sugar, which is prob ably in the form of a soluble calcium saccharate, it=is precipitated as an insoluble calcium saccharate by heating the waste water to a temperature of from to859 C. and subsequently separated from its mother liquor 'by filtration or sedimentation or a combination of both.

The present invention relates to the last mentioned precipitation step of the process, andits main object is as stated herei-nbefore,

to facilitate, and expedite the final separation by which the precipitated sugar%'ifsre covered'from the liquor. a By the way of further explanation, it may be stated that our improved process, takes the place of either, of two methods which heretofore were generally employed to recover the sugar-contents of thecold waste waters. 1 w

One of these methods commonly known as the batch process consists in heating the solution in .a tank usually equipped-'w-itha stirring device, the heat being preferably applied by means of: steam introduceddi-p rectly into the solution; andthe other method consistsin causing the solution to I flow' progressively from one to another of a seriesfof two' or more itanks and heatingthe tanks by introduced steam insucha 7 from the first'tan'k into whi'ch the'cold Waste is originally fed, to tlie'last tankwofflthei series which is heated to the'usual-maximum I temperatureof frojm',80 to85-- In both methods the heat precipitates the sucrose and lime contained inthe cold waste, in small" particles which are subsequently" separated from-the-mother liquor by filt'ra-X tion or sedimentation but owing to the fineness 'of the particles, jtheirfseparation a difiicult,costlyand slow procedure, as is indictated by thefact that the average precipi l .-three tofourfeet per hour. a

By the'use of our improved method of forming the precipitate the size of the particlesis greatly increased and their separation from the, liquor is proportionately accelerated. Incarrying our invention into effect; the cold Waste Water diluted With twenty or. more equal volumes of mother 1 liquor from "the hot saccharate precipitation reaction,- and; the mixture;i s heated to the usual temperature of from 80 to 85 C. r The concentration of the precipitable con- Cstituents ofthecold Wasteresiduum ofthe 4 Steffens process, is approximately 1% of the .materialby Weight and if I: one volume of this is dilutejcl with, for example; voln umes of barren"solution:obtainedin a prior, e precipitationaction, the "concentration of the a; precipitable constituents of. the pregnant solution is lowered in the nixtureto approx- 'imatel'ylQ.05%; by weight. Owing to this ilowerfconcentrationa lesser number of precipitate'nuclei are formed'when the mixture isgsubjected to the precipitatingheat, and

tate settles at a rate but seldom exceeding feachnucleusyvvill separately increase in size] unt lthe presolp' tatmg, react on 1s coin- 7 ,pleted. v I p The consequentlyincreased rategof se'divious'ly facilitates and expedites' their subse l 'qu'ent' separation from the llmother liquor. andxthe improved'proc'ess-of forming the precipitate therefor resultsin economy, in

I thejrequired-apparatus and in greaterequip ment efii'ciency While permits a higher recovery of granulated sugar per' pound of .sugar' precipitated. l

proved p roeess5;may range from i hour up to 25ffeet' per hour. Y

- o 0 u I 1 lime, whichj under the lmposed condltions sugar; which zunderodifierent fconditions' i might. be precipitatedf and that since all, of

charged, it may alsojcontain an amount of "precipitated matter; f Thefp'resence: of these i t substances -ho vever,{ does not noticeably in- I e f reavith; th QP m p i e and solutionfl nay be-correctly;gdefined as being,

mentation offthe "precipitated particles "ob installation, maintenance and operation of It has been found in -actual" practice that the rate of sedimentation of-particlespr'e- 'cipitated under the oonditionsxof our im-' -Theterm; barren-solution as employed inithiswdescriptionrefers togas'solution sub- I ,although it mayi and-inpractice; often does 'ponents ofthe: pregnant solution, sugar and are not"precipitated. It follows that the" YQjarrenQsolution;a may-contain lime and 1 the precipitate. may {not be;v immediately 1disarre {i 1-1 LPurPQs it -W a aine 1: Y i 1; As 0 n ;,the rior 1 methodso'fforming the @1191; saccharate precipitate,hereinbefore de-= Q1 52 scribed, f the soutionflis heated? preferably,

the introduction of live steam. It is obvious that this steam will to some extent dilute the infiovving material but this dilu- 7 tion is merely incidental and not suflicient to step of the process herein described and included in the claims refers onlyto aydegree of dilution suflicient to produce the desired size of the precipitated particles;

In order to-re'nder the process continuous, we have combined With a continuous feed of pregnant material a concurrent discharge of barren solution carryingthe precipitate in suspension. The continuous process requires the constant presence of a quantity of barren solution into which the pregnant solution is introduced in' comparatively small quantities compensated by the concurrent discharge of liquor and precipitate, and

it is from a practical point of View desirable that mechanical means he provided to reffect a thorough intermixtur'e of thefpregnant liquor with the barrenliquor in 'a circulatory movement of the latter.

The apparatus illustrated in Figure 2 of the drawings provides a simple. and efi'ective mediumto conduct the continuous process as hereinabove described. r

tank 5 is bymeans of an open-ended funnel 6 divided into a central mixing zone 7 and a surrounding annular precipitation Zo1ie'8. A'rotary ship propeller Sin the ;lovver end-portion of the funnel is adapted tofeffect a circulatory movement of a liquid in the tank-upwardly in the precipitating zoneand downwardly through the funnel,

and the cold Waste is continuouslyfintro duced into the funnel immediately above the propeller. through a numberof valvecontrolled pipes 10. i I i introduced through; perforated 1 circular pipes 12 in connection with upwardly ranging feedpipes l3, and radial baflies 14 and 15 in thefunnel and the precipitation'zone prevent the material from swirling in a horizontaldirection'. I i i a @An' outlet 16in the-outer wall of the tank provides an overflow through which the surplus liquor'iand suspended precipitate are sc a g p 1 r j In the operation of "the-apparatus, the tank isfilled-to the leveldetermined by its overflow with; barren solution obtainedjby then-precipitation of sugar and lime from a volume' of cold lwastewater Withwhich the tank is initially-charged,

- nae: the. tankfis thus; supplied {with a L barren solution; containing precipitated but practically no precipitable matte'r fresh cold; waste o is; introduced into the, mixing y The precipitating zoneis heated by steam and it Will be understood that the dilution The mixture of pregnant cold waste and barren solution is heated in the precipitation zone to the required temperature of from to C. with the result that the precipitable matter of the cold waste, distributed in a mixture of larger volume is precipitated. in crystals or flocs which owing to the lower concentration are increased in size.

The surplus liquor and precipitate are continuously discharged through the overflow opening 16 so that subject to a continuous feed the process of forming the hot saccharate precipitate is carried on without interruption.

In order to minimize precipitation by the heat of the stream of barren liquor in the funnel before the cold waste enteringthe mixing zone through the pipes 10, is thoroughly diluted it is desirable that the feed be entered into the circulating stream in as close proximity to the mixing zone defined by the space around the propeller, as is practical and that immediately upon diffusion of the feed the stream be caused to" enter the precipitation zone.

'It will be evident that the precipitating action is governed by the velocity of thecirculating stream in ratio to the quantity of cold waste entered in the stream in a given period of time and to the. degree of heat imparted to the mixture by the steam introduced into the precipitation zone through the perforated pipes and that in consequence the process is under perfect control of the operator and may be regulated at will in accordance with varying conditions.

A stream-velocity of 800 cubic feet per minute, with a feed velocity of approximately 40 cubic feet per minute in a diluting liquor 20 times its volume and a heat of from 80 to 85 C. have produced highly satisfactoryresults under normal conditions. Having thus described our invention, what we claim and desire to secure by Letters Patent is: r f

l. The process of precipitating precipi table matter in cold Waste water, consisting in diluting the waste water to reduce the concentration of precipitable matter contained therein to one-twentieth or less of its original concentration, and subjecting the mixture to a precipitating heat. V

2. The process of precipitating precipitable. matter in cold waste water, consisting in mixing and diluting the waste water with twenty or more times its volume of a comof crystals or flocs in the mixture when the latter is heated to effect a precipitation of the solution-contents, the crystals or flocs functioning to increase the rate of sedimentation of the precipitate and thensubjecting the mixture to a precipitating heat.

' 3. The. process of precipitating precipi' table matter in cold waste water, consisting "in mixingand diluting'the waste water with a comparatively barren solution containing, non-sucrose impurities, said barren solutionbeing adapted to induce the formation of crystals or flocs in the mixture when the latter is heated to effect a precipitation of the solution-contents, the crystals or flocs functioning to increase the rate of sedimentationof the precipitate, and subjecting the mixture to .a precipitating heat.

4:. The process of precipitatingv precipitable matter in cold waste water, consisting in mixing and diluting the waste water with a larger volume ofa comparatively barren solution, said barren solution being adapted to induce the'formation of'crystals or'flocs' in the mixture when the latter is heated to i effect a precipitation of the solution-contents,- the'crystals or flocs functioning to in creasetherate of sedimentation of the precipitate, and subjecting the mixture to a precipitating heat. r i

5. The process of precipitating *precipitable matter in cold waste water, consisting in the dilution with. the aid of mechanical intermixing of the waste water with a comparatively barren solution, said barren solution being adapted to inducethe formation of crystalsor 'fioc's in the mixturewhenthe latter is heated to effect a precipitatio'n'of the solution-contents, the crystals or flocs' functioning to increase the rate 'of sedimentationof the'precipitate, and subjecting mixture to a precipitatingheat. v

-6. The process of precipitating precipitable matter in cold waste water, consisting.

in' feedingthe waste waterinto'a -pa'ssing current of a comparatively, barren solution, said barren solution being adapted to m ducetheform'ation of c'rystalsor flocs 1n the IOU mixture when the latter is heatedtoeifect a precipitation ,ofthe solution-contents, the crystals or flocs functioning to increase the rateof sedimentation of the precipitate, and subjecting the mixture to a precipitating heat. i

7. The process of precipitating precipi ren solution, said barren solution being adapted to induce the'formation of crystals or flocs in the mixture when the latter isheated to effect a precipitation of the solution-contents, the crystals or flocsfunction- 'ing to increase the rate of sedimentation of the precipitate, and subjecting the mixtur .to a precipitating heat.

8. The process of precipitating precipitable matter in cold Waste Water,'consisting ii -feeding the wastewater at a plurality of n points .into a moving. current of c0n1paratively' barren solution, said barren solution beingadapted toinduce the formation of crystals or flees in themixture When the v latter is heated ,toefiiect a'precipitation'ofthe solution-contents, the crystals or flocs functioning to increase the rate of sedimem, tation of the precipitate, and subjecting the mixture to a precipitating heat. v 9.The process ofprecipitating precipitable lnatterxin cold Waste Water, consisting in feeding theywaste Water at a plurality 15 of points into a mechanically agitated current of comparatively barren solution,sa,id

barren, solutionlbeing adapted to induce the p I formation of crystals or floc s ingthe mixture hen-the latter is heatedto effect a precipie 520 tation of thesolution -contents, the crystals or flocsfunctioning to increase the rate of sedimentation of: the precipitate, and subecting the lmixtur'eito a precipitating heat. 10. The process of precipitating 'precipi table matter in cold ,Waste .water, consisting in mixing and .dilutingthebwaste Water with p a hot saccharate 1 precipitate solution, said solution being adapted to induce the formation of crystals-orifiocs in the mixture when the latter isheated to effect a precipitation of the solution contents, the crystals or'fiocs functioning t'oincrease the rate of sedimentation of the precipitate, and subje'cting the mixture toa precipitating heat; 7

3a "11;. The process of; precipitating the Vprecipitablelimefrorna solution, consisting'in' 1 mixing and. diluting the solution with a in 1 solution containing dissolved lime said solution being adapted'to induce the formap 50 tion of crystals orflocs in the mixture when theflatter is heated to efiecta precipitation offthe"soluti'on contents, the crystals or flocs functioning to increase the rate of sedimen; tatio ft p e p at d. j ingih j mixture to precipitating heat.

a v t sfi mdl ywh re e haveafiixed our 1 signatures; j v f I a J, RALBHWV. SHAFOR, 

